1. Field of the Invention
The present invention relates in general to lock devices that lock one member to the other member, and more particularly to the lock devices of a type that locks a seat back or seat cushion of a vehicle seat relative to a body of a vehicle. More specifically, the present invention is concerned with the lock devices of a type that is able to obtain an improved locked condition relative to a striker.
2. Description of Related Art
Hitherto, various lock devices have been proposed and put into a practical use in the field of seats of motor vehicles. Some of them are of a type that can lock a pivotal seat back at a given angular position relative to a seat cushion mounted on a floor of the vehicle.
For providing a seat occupant with an assuredly safety ride on the vehicle, some of the lock devices of the above-mentioned type are equipped with an improvement in assuring a locked condition of the lock device (or lock unit) relative to a fixed striker. Actually, if the lock device fails to exhibit a satisfied locking work to the striker at the time of vehicle collision or the like, the seat back to which the lock unit is mounted would be released from the striker causing the seat occupant to get into unsafe situation.
For eliminating such drawback, Japanese Laid-open Patent Application (tokkai) 2011-255799 proposes a lock device that can lock a seat back of a vehicle seat at a given angular position (viz., in-use position) relative to a striker fixed to a vehicle body. The lock device (or lock unit) disclosed by this publication comprises generally a base plate that has a striker receiving recess, a latch plate that has a striker latching recess and is rotatably connected to the base plate to rotate between a striker latch position and a striker unlatch position, a cam member that is rotatably connected to the base plate and functions to turn the latch plate latching the striker to a lock position and a ratchet pawl that is rotatably connected to the base plate and functions to lock the latch plate taking the lock position. That is, when the lock unit assumes a locking condition locking the striker for locking the seat back at the given angular position (or in-use position), the lock unit shows such a condition that the striker in the striker receiving recess is latched by the latch plate and at the same time the latch plate is locked at the striker latch position by the ratchet pawl. The improvement proposed by the publication is to provide a lower edge of the striker latching recess of the latch plate with an inclination. Due to provision of this inclination, when the lock unit assumes the locking condition, a rectangular locking space for the striker that is defined by both a bottom portion of the striker receiving recess and the lower edge of the striker latching recess can have a narrowed exit for the striker. With this narrowed exit, undesired disengagement of the striker from the lock unit, which would be caused at the time the vehicle collision or the like, is suppressed.